gms | German Medical Science

Objectives: It is reported that 70% of the Knee OA patients have cartilage degeneration isolated to the medial and patellofemoral compartments. Majority of these patients undergo total knee replacements (TKR). A customized, individually made bi-compartmental knee replacement (BKR) treating OA at medial/lateral and patellofemoral compartments could be a possible treatment of such disorders. It is surmised that the BKR knee will have similar knee mechanics to that of a normal healthy knee during daily activities. There are no in vivo biomechanical comparisons between a BKR limb and a limb with an off-the-shelf TKR.

The objective of this study is to examine the differences in knee mechanics between three groups of participants during walking: (1) patients with BKRs, (2) patients with TKRs, and (3) healthy controls.

Methods: To date, 23 participants have been recruited. Seven patients (63±10 yr.; 100±43 kg; 1.73±0.12 m) received TKRs (Persona, Zimmer Inc.) (post-op: 14±5 mo.). Four patients (63±7 yr.; 93±18 kg; 1.66±0.06 m) received BKRs (iDuo, ConforMIS Inc.) (post-op: 19±4 mo.). Twelve healthy participants (57±6 yr.; 82±12 kg; 1.75±0.11 m) served as controls. Participants walked at a self-select speed in a gait laboratory. 3D motion capture was performed at 100Hz and ground reaction forces were collected at 2000Hz. Knee joint kinematics and kinetics were calculated during the stance of walking. MANOVA was performed. P=0.05.

Results: Table 1 [Tab. 1] shows the means and SDs of the walking speed and sagittal plane knee mechanics of the three groups. No significant differences in walking speed, peak knee extensor moment, peak knee power absorption, and peak knee power production between the BKR and control groups (P>0.05). Compared to the control group, the TKR group showed slower walking speed, less peak knee extensor moment, less peak knee power absorption and production (P<0.05); Compared to the BKR group, the TKR group demonstrated less peak knee power absorption and production (P<0.05); In addition, the TKR group showed a trend of less peak knee extensor moment than that of the BKR group (P=0.08).

Discussion and Conclusion: Normal walking speed and sagittal plane knee mechanics appear to be achievable outcomes with customized BKR surgeries. In this study, the BKR patients demonstrated comparable walking speed and peak knee extensor moment and power to the healthy control participants during stance of walking. Off-the-shelf TKR patients walked significantly slower than healthy controls with less knee extensor moment and power produced. In addition, compared to the BKR knees, the off-the-shelf TKR showed deficits in peak knee extensor moment and power during walking. It is possible that the weakness in TKR knee strength may be associated with the traditional off-the-shelf TKR design. In conclusion, a customized BKR design could provide adequate support to knees to perform normal walking.